Voltage converters, comprising buck converter, boost converter and buck-boost converter, are widely adopted to convert an input voltage to a desired output voltage in a power management system. In real application, a boost converter or a buck converter is usually adopted to provide a positive output voltage, and a buck-boost converter is usually adopted to provide a negative output voltage. In an application both the positive voltage and the negative voltage are needed, a combination of the boost/buck converter and the buck-boost converter are adopted.
However, the conventional combination of the buck/boost converter and the buck-boost converter is merely an integration of two independent voltage converters, and needs two inductors, which results in large size and high cost.